The major objective of the AIDS Dementia Center is to map the course of HIV on the nervous system, to find identifiers of the earliest neurological involvement and predictors of neurologic decline in adults and children. The activities of the Core and five Projects described projects are very closely interrelated to develop the mission of the center. The cohorts of subjects are already established. Projects are: Project 1- Detailed longitudinal evaluation of adult HIV infected subjects, with careful documentation at six month intervals of neurological, neuropsychological psychiatric, cerebrospinal fluid and hematological examination. Participation in multicenter protocols of antiretroviral agents for the prevention of the onset of neurological disease and its treatment if it does occur. A percentage of the subjects in this Project will also be evaluated in Projects 1-4) Project 2- Similar studies, without CSF, on HIV infected hemophiliac children and adolescents. Project 4- Detailed clinical neurophysiological examinations of these two cohorts, to include: routine and quantitative EEG; visual, brainstem auditory, P3 cognitive and somatosensory evoked potentials; in the adults, nerve conduction and fiber density studies. Project 5- Evaluation of the same subjects with magnetic resonance imaging and magnetic resonance spectroscopy. The objectives of the Program will be achieved by correlation of the results of the multifactorial evaluations, by using subjects as their own controls and by comparison with normal controls.